- 1 cup sliced blanched almonds
- 2 tablespoons granulated sugar
- 1 cup confectioners' sugar, plus more for dusting
- 3 large egg whites
- Pinch of salt
- 1/2 teaspoon pure vanilla extract
- Zest of 1 lemon, plus 1 teaspoon fresh lemon juice (preferably Meyer)
- 6 tablespoons heavy cream
- 2/3 cup chopped bittersweet chocolate
- 1 teaspoon instant espresso powder
Process almonds and 1 tablespoon granulated sugar in a food processor until finely ground. Transfer to a medium bowl; stir in confectioners' sugar. Put egg whites and salt into bowl of mixer fitted with whisk attachment; beat on medium until soft peaks form. Add remaining granulated sugar; beat until stiff peaks form. Mix in vanilla and lemon juice. Fold in almond mixture in 2 batches. Stir in zest.
Preheat oven to 300 degrees. Put batter in a pastry bag fitted with a 1 1/2- inch round tip (Ateco tip #803 or #804); pipe 2-inch rounds onto a nonstick baking sheet. Bake until golden and set, about 15 minutes. Let cool on a wire rack.
Bring cream to a boil in a pan. Pour over chocolate and espresso in a heatproof bowl; whisk. Transfer to freezer and stir occasionally until thickened, about 6 minutes.
Spread 2 teaspoons filling onto bottom of half of the cookies. Sandwich with remaining cookies. Dust with confectioners' sugar.